This invention relates generally to the art of alloys and more particularly to a novel nickel aluminide alloy having improved welding characteristics.
The following U.S. patents have issued on nickel aluminide alloys:
4,612,165 Ductile Aluminide Alloys for High Temperature Applications
4,711,761 Ductile Aluminide Alloys for High Temperature Applications
4,722,828 High-Temperature Fabricable Nickel-Iron Aluminides
4,731,221 Nickel Aluminides and Nickel-Iron Aluminides for use in Oxidizing Environments
4,839,140 Chromium Modified Nickel-Iron Aluminide Useful in Sulfur Bearing Environments
5,108,700 Castable Nickel Aluminide Alloys for Structural Applications
5,413,876 Nickel Aluminide Alloys with Improved Weldability
Each of these patents, which are hereby incorporated by reference, disclose only major alloy elements. For example, the alloy called IC221, disclosed in U.S. Pat. No. 4,731,221 is a composition of Nixe2x80x9416.1A1xe2x80x941. OZrxe2x80x948.0Cr at %.
In reality, alloys produced and processed by commercial practices contain other alloying elements. For example, these elements may occur in the finished alloy due to contamination of scrap materials used in melting, or through the interaction of liquid alloy with molding materials used to make metal castings. Some of the unintentionally added elements, termed xe2x80x9cminor elementsxe2x80x9d, may have little or not adverse effect on the subsequent properties of an alloy. Other of these unintentionally added elements may be highly undesirable.
Minor elements that are known to produce undesirable effects in high-strength, high-temperature Ni-based alloys, like nickel aluminide alloys, include boron, carbon, silicon and sulfur. Boron may be intentionally added to nickel aluminide alloys to improve ductility. However, high boron concentrations, above about 0.01 wt %, are known to cause difficulties with certain properties such as weldability. Experience shows that carbon, silicon and sulfur are common minor elements in nickel aluminide alloys prepared under industrial conditions. Concerns about the possible detrimental effects of these elements leaves a need to more thoroughly define the desirable chemical composition ranges of nickel aluminide alloys such as IC221.
It is an object of this invention to provide a novel nickel aluminide alloy.
It is further an object of this invention to find such an alloy with improved welding characteristics.
These as well as other objects are accomplished by an alloy comprising a nickel aluminide alloy having improved welding characteristics comprising about 6-12 wt % aluminum, about 6-12 wt % chromium, about 0-3 wt % molybdenum, about 0-6 wt % zirconium, about 0-0.02 wt % boron, about 0.01-0.15 wt % carbon, about 0.01-0.20 wt % silicon, about 0.001-0.010 wt %, sulphur, about 0.01-0.30 wt % iron, and balance nickel.